Fix issue where if you drag the last element of `ReorderableList` and put it in the same index, a `Null check` error arises. This happens as index in `_items` is out of bounds (when `reverse: true`). Fix is to check if last element, dragged element and drop index is same, and return as nothing has changed. Find this video attached.

https://github.com/flutter/flutter/assets/84124091/8043cac3-eb08-42e1-87e7-8095ecab09dc

Fixes issue #132077